Different methods for preparing catalysts are known from the prior art. In the art there are several types of catalysts which differ both in structure and materials. One specific type of catalyst consists of a metal substrate on which a catalytically active layer has been deposited.
Several methods for the deposition of the active layer are known from the prior art. Typically, the catalytically active layer is added to the metal substrate by washcoating using alumina or another metal oxide slurry containing the catalytically active metals in the form of salts, oxides or elemental metals. Substrates can also be first washcoated with a metal oxide slurry, and then a catalyst metal addition can be performed using traditional methods, such as impregnation. In these methods it is difficult to control the size of the metal particles, dispersion or the thickness of the layer. Thus, excessively high metal loadings have to be used in order to obtain high catalytic activity. It is beneficial to decrease the metal loading in catalytic reactors, for instance, due to the fact that catalytically active metals are in many cases getting more and more expensive and many of them are rare and strategic metals.
Further, from the prior art is known an atomic layer deposition (ALD) method for coating different materials.